When testing an electronic component during or after its manufacture, the testing procedure may involve corner testing. During a corner test, a device under test (DUT) is tested for its operability in situations, where several of its operating parameters are simultaneously at extreme levels, even though each of the values of the respective operating parameters lies within the specified range for that operating parameter. A corner case therefore corresponds to a problem or a situation which only occurs when several operating parameter values are “on the edge” of their rated range, i.e. when several operating parameters assume their corresponding minimally or maximally rated values (extreme values). Corner cases are often harder and more expensive to reproduce, test, and optimize because they require extreme configurations in multiple operating parameters. In addition to that, being guided by the belief that the chances for their product being operated at multiple simultaneous extreme settings is very slim, some manufacturers may tend be reluctant to test corner cases thoroughly.
Corner tests are often used in pre- and post-Si (silicon) verification of semiconductor devices to ensure functionality of the DUT under all constraints given by the specification, process variations and other deviations from nominal conditions. These tests are faced with the problems stated above and in addition, owing to the usually large number of operating parameters, they consume a lot of valuable testing time. Exhaustive or complete testing with 100% coverage of all corner cases involves testing and/or simulating the device under all possible combinations of minimum and maximum operating parameters. The number of such tests and/or simulations rises exponentially with the size of the verification space, i.e. the number of considered operating parameters of the device, and in consequence, so does the testing and/or simulation time. The test time can of course be reduced by incomplete testing which, however, may lead to undetected application failures. Monte Carlo tests may explore the full verification space but only reach 100% (average) coverage of all corner cases for an infinite number of tests and/or simulation runs.